Method and apparatus for the gaseous reduction of iron ore to sponge iron

ABSTRACT

Method and apparatus for reducing particulate metal ore, e.g., iron ore, to metal particles, e.g., sponge iron, in a vertical shaft, moving bed reactor having a reduction zone and a cooling zone wherein separate streams of reducing gas and cooling gas are used in the reduction and cooling zones, respectively, and means are provided for minimizing commingling of the two gas streams. In one embodiment a differential pressure controller is used to maintain substantially equal the gas pressure at the bottom of the reduction zone and the gas pressure at the top of the cooling zone. In another embodiment the flows of inlet gas to and outlet gas from the cooling zone are controlled to maintain these two flows substantially equal. Either or both of the reducing gas and cooling gas may be recycled in a closed loop.

3,601,381 8/1971 3,369,888 2/1968 2,609,288 9/1952 3,348,941 10/19671,401,222 12/1921 2,528,553 11/1950 2,635,957 4/1953 Kalling et a1 75/35Unit d. States Patent (1 1 Celada et a1.

' 4] METHOD AND APPARATUS FOR THE GASEOUS REDUCTION OF IRON ORE TOSPONGE IRON [75] Inventors: Juan Celada; David Villarreal;

- Patrick W. MacKay, all of Monterrey, Mexico [73] Assignee: FierroEsporria, S.A., Monterre Mexico [22] Filed: Dec. 16, 1970 I [21] Appl.No.: 98,612

Related US. Application Data [63] Continuation-impart of Ser. No.55,161, July 15', 1970, abandoned.

[52] US. Cl. 75/34, 75/35 [51] Int. Cl C211) 13/00 [58] Field of Search75/34, 35

[56] References Cited UNITED STATES PATENTS 2,862,808 12/1958 De .lahn75/34 8O Comma 6A5 [4 1 Oct. 16, 1973 9/1957 Segre. 75/35 6/1965 VonBogdandyp. 75/34' 7 OTHER PUBLICATIONS Perrys Chemical EngineersHandbook; 4th Ed.;

McGraw-l-lill; 1963; page 22-99.

Primary ExaminerL. Dewayne Rutledge Assistant Examiner-M. J. AndrewsAtt0rneyCurtis, Morris & ,Safford [57 ABSTRACT -Method and apparatus forreducing particulate metal ore, e.g., iron ore, to metal particles,e.g., sponge iron, in a vertical shaft, moving bed reactorhaving areduction zone and a cooling zone wherein separate streams of reducinggas and cooling gas are used in the reduc tion and cooling zones,respectively, and means are provided for minimizing commingling of thetwo gas streams. In one embodiment a differential pressure controller isused to maintain substantially equal the gas pressure at the bottom ofthe reduction zone and the gas pressure at the top of the cooling zone,In another embodiment the flows of inlet gas to and outlet gas from thecooling zone are controlled to maintain these two flows substantiallyequal. Either or both of the reducing gas and cooling gas may berecycled in a closedloop.

20 Claims, 3 Drawing F igures AAAAAAA METHOD AND APPARATUS FOR THEGASEOUS REDUCTION OF IRON ORE TO SPONGE IRON This application is acontinuation-in-part of pending application Ser. No. 55,161 filed July15, 1970, now abandoned.

This invention relates to the gaseous reduction of particulate metalores to metals in particulate form in a moving bed, vertical shaftreactor, and more particularly, to an improved method and apparatus forcontrolling the reduction of the ore and the cooling of the resultingmetal particles. In the following description the method and apparatusare illustratively described as applied to the reduction of iron ore tosponge iron. However, as the description proceeds it will be evident tothose skilled in they art that the invention is also applicable to thetreatment of ores other than iron ore.

Broadly speaking, the production of sponge iron in a vertical shaft,moving bed reactor ordinarily involves two principal steps, namely,reduction of the ore in a reduction zone with a suitable hot reducinggas, typically a gas largely composed of carbon monoxide and hydrogen,at temperatures of the order of 850 to l,l C., preferably 900 to 1,000C., and cooling of the resulting sponge iron with a gaseous coolant to atemperature of the order of, say, 100 to 200 C., preferably below 100 C.In a number of the previously proposed processes, cooling of the spongeiron is effected by passing a portion of the reducing gas at relativelylow temperature upwardly through the cooling zone of the reactor wherebythe reducing gas temperature is increased and the temperature of thesponge iron is reduced, and then introducing additional hot reducing gasat the bottom of the reduction zone of the reactor.

This mode of operation is subject to the disadvantage that it does notpermit fully independent control of the reduction and cooling steps ofthe process. The sponge iron product is commonly used as the charge, orpart of the charge, to an electric steel-making furnace and it has beenfound that when used for this purpose the sponge iron should desirablybe carburized. Such carburization can be conveniently carried out byusing as a coolant a carbon-containing gas which cracks as it passesover the hot sponge iron and deposits carbon thereon. However, in orderto achieve a particular desired degree of carburization, as well as thedesired cooling effect, the composition and flow rate of the coolant gasshould be controllable independently of the conditions existing in thereduction zone of the furnace.

It is further important that the sponge iron be sufficiently cooledbefore it is discharged from the reactor, since if it is exposed toatmospheric air at too higha temperature, it tends to re-oxidize. Forthis reason also it is desirable that the composition, flow rate and/ortemperature of the gases in the reduction and cooling zones beindependently controllable. However, if different gas streams are usedin the two zones, there is a tendency for the gases to commingle at thejunction of the two zones and produce indeterminate changes in theproperties of one or the other of the two gases or both.

It is accordingly an object of the present invention to provide animproved method and apparatus for achieving essentially independentcontrol of gas flow in the reduction and cooling zones of a verticalshaft, moving bed, ore reduction reactor. It is another object of theinvention to provide a method and apparatus which permits such controlwhile minimizing commingling of the two gas streams. Other objects ofthe invention will be in part obvious and in part pointed out hereafter.

The many objects and advantages of the present invention can best beunderstood and appreciated by reference to the accompanying drawingswhich illustrate sponge iron production systems incorporating severalembodiments of the apparatus invention, which apparatus is capable ofbeing used to carry out the method of the invention.

In the drawings:

FIG. 1 illustrates diagrammatically a sponge iron production systemwherein separate gas streams are fed to the reduction and cooling zonesof the reactor and commingling of the gases is minimized by establishinga substantially zero pressure difference between the reduction andcooling zones;

FIG. 2 shows a similar system wherein commingling of the gases isminimized by directly controlling the gas input flow to and gas removalflow rate from the cooling zone; and,

FIG. 3 shows a system wherein the reducing gas and cooling gas may befed to either the top or bottom of the reducing zone and cooling zone,respectively.

Referring to the drawings, and particularly FIG. 1, numeral 10 generallydesignates a vertical shaft reactor having a reduction zone 12 in theupper portion thereof and a cooling zone 14 in the lower portionthereof. The reactor 10' is suitably heat insulated and is interiorlylined with a refractory material in a manner known in the. art.Particulate ore to be treated is introduced into the reactor 10 througha charging pipe 16. The ore to be charged may be in the form of eitherlumps or preformed pellets. It flows downwardly through the reductionzone wherein it is largely reduced to sponge iron by upwardly flowingreducing gas, then through the cooling zone 14 wherein it is cooled byupwardly flowing cooling gas and leaves the reactor through the outletpipe 18.

At the junction of the reduction and cooling zones there is an internalfrusto-conical baffle 20 which guides the downwardly flowing oreparticles to a conduit 22 leading to the cooling zone 14. The baffle 20extends through the wall of the reactor and forms part of an annularplenum chamber 24 extending around the periphery of the reactor andproviding a means for feeding the incoming reducing gas to the reduction.zone through a space between the reactor wall and the baffle 20.

Near the bottom of reactor 10 there is a frustoconical baffle 26 which,together with the reactor wall, defines an annular space 28 throughwhich the cooling gas flows to the body of ore particles in the coolingzone 14. If desired, the reactor 10 may be operated at an elevatedpressure in which event the ore is fed at the top of the reactor andsponge iron removed from the bottom of the reactor by using suitablefeed and discharge lower portion 34 of the reformer wherein they areconverted to a gas mixture consisting largely of carbon monoxide,hydrogen and water vapor. The gas mixture then flows through pipe 36 toa quench cooler 38 wherein the gas is quenched to remove most of thewater vapor therefrom. Upon leaving cooler 38, gas flows through pipe 40and pipe 43 to a flow controller 44 which operates to establish apredetermined flow of reducing gas to the reactor.

In thesystem shown in FIG. 1, the reducing gas is heated to the desiredreducing temperature of, say,

' 900 to 1,000 C. in several stages. Thus the controlled flow of gasafter leaving controller 44 passes through a heat exchanger 46 in heatexchange contact with the exit cooling gas as will be further describedbelow, and thence through a coil heater 48, which may be gasfilled orotherwise heated, to raise the reducing gas temperature to the order of700 to 850 C. Since the reducing temperature should desirably be of theorder of 900 to l,OO C., the temperature of the reducing gas leavingheater 48 is further increased by adding a relatively small. amount ofair or oxygen thereto through pipe 50 and burning a small amount of thereducing gas to raise the temperature of the mixture to the desiredvalue. Especially in cases where air is used as the oxidant, the oxidantis desirably preheated to approximately the temperature of the reducinggas with which it is mixed. Such preheating can be effected, forexample, in a coil heater such as the coil heater48. The addition of airor oxygen to the reducing gas may be ef: fected, for example, asdisclosed in U. S. Pat. No. 2,900,247. The reducing gas as thus preparedflows into the plenum chamber 24 and upwardly through the reduction zone12 as previously described.

Spent reducing gas leaves the reactor through discharge connection 52and flows to a water-cooled quench cooler 54. Upon leaving the quenchcooler 54, the gas stream may be divided into several sub-streams. Thusif it is desired to recycle a portion of the reducing gas, the recycledgas may be caused to flow through pipe 56 containing compressor 57 andregulating valve 60 to pipe 43 wherein it is combined with the freshlyprepared reducing gas. The compressor 57 may be designed to have acapacity somewhat greater than that required to recycle the desiredamount of reducing gas and may be provided with a by-pass 58 and.pressure controller 59 that operate to maintain the compressor dischargepressure substantially constant.

Another portion of the spent reducing gas may flow through a check valve62 and pipe 64 containing valve 66 to a storage container for fuel gas.Spent reducing gas that is neither recycled nor passed to the fuelstorage flows through pipe 68 to a vent stack 70. Pipe 68 is providedwith an automatic pressure controller 72 for maintaining a suitable backpressure on the gas reduction system. It will be understood that all ofthe spent reducing gas may be caused to flow through any one or more ofthe three paths described above. However, for economical operation atleast a substantial part of the spent reducing gas should be recycled.

As indicated above, the reduced ore iscooled by a cooling gas in thecooling zone 14 of the reactor. Referring to the lower left-hand portionof FIG. 1, cooling gas enters the system through a pipe 80 provided withan automatic flow controller 82. A wide variety of cool- I ing gases maybe used including hydrogen, carbon monoxide, mixtures thereof, methaneor other hydrocarbon gas, carbon dioxide or nitrogen. The choice of acooling gas depends upon such factors as whether it is desired tocarburize as well as cool the sponge iron and whether the spent coolinggas is to be later used in some part of the reducing gas system.

Upon entering the cooling gas system the cooling gas flows to acompressor 84 having a by-pass 86 provided with a pressure controller 88which, like controller 59, operates to maintain a constant pressure atthe compressor discharge. The cooling gas then flows through pipe 90which is provided with an automatic flow controller 92 to the annularspace 28 in reactor 10, thence upwardly through the cooling zone 14 toan annular space 94 defined by baffle 20, conduit 22 and the wall of thereactor. As indicated above, carburization of the sponge iron can beeffected'in cooling zone 14 by using a carbon-containing cooling gasthat is cracked in contact with the hot sponge iron to deposit carbonthereon. The, heated cooling gas leaves the reactor through pipe 96 andflows through a conventional dust separator 98 to the heat exchanger 46wherein it gives upa portion of its heat to the reducing gas asdescribedabove.

From exchanger 46 the cooling gas flows to and through a water-cooledquench cooler 100 and is then recycled through pipe 102 containing valve103 to the inlet of compressor 84. A portion of the recycled gas isdiverted through pipe 104 and flows to the spent reducing gas portion ofthe system shown near the top of FIG. 1. As illustrated in the drawing,this diverted gas may flow through a pipe 106 containing valve 108 tothe reducing gas loop or through pipe 110 containing valve 112 to thecombustible fueld storage or the vent stack 70. While it is generallydesirable to establish a closed cooling gas loop as just described, inparticular cases valve 103 can be closed and all of the cooling gasleaving quench cooler 100 may be caused to flow through pipe 104.

As indicated above, the present invention provides method and apparatusfor minimizing commingling of the reducing gas and cooling gas in thereactor. Referring to the right-hand portion of FIG. 1, a differentialpressure controller is provided which is made responsive through pipe122 to the pressure is plenum chamber 24 (designated P,) and through apipe 124 to I the pressure in annular space 94 (designated P Thedifferential pressure controller 120 establishes a signal, e.g., apneumatic pressure, which is a function of the difference betweenpressures P, and P and this signal is used to adjust the setting of apressure controller 126 in the pipe 104 and thereby regulate the backpressure in the diverted cooling gas pipe 104 in such manner as to makepressure F substantially equal to pressure P,. Thus the interior ofconduit 22 becomes a substantially isobaric zone and commingling of thereducing gas and cooling gas is minimized. It is further desirable,although not essential, that the pressure P, be maintained constant andthat the flow through pipe 104 be adjusted to bring the pressure P to avalue' equal to P,. To this end, an automaticpressure controller 128 ismade responsive to the pressure P, through pipe 130 and the controlleroutput is conducted through pipe 132 to the pressure controller 72 toadjust the set point of the latter controller in such manner that thespent reducing gas is vented at a rate such as to maintain the pressureP, substantially constant. It has been found that by maintaining thepressure P, constant in this manner the pressure within conduit 22 canbe maintained more nearly isobaric.

It will be evident from the foregoing description that the apparatusillustrated permits the use of separate reducing gas and cooling gasloops including the reduction zone and cooling zone of the reactor,respectively. The composition, flow rate and temperature of the reducingand cooling gases can be independently controlled so that each gasperforms its desired different function in an optimum manner and to anoptimum extent and the overall efficiency of the reactor is enhanced.

Turning now to FIG. 2 of the drawings, the system there shown is largelythe same as that shown in FIG. 1, and hence only the differences betweenthe system of FIG. 2 and FIG. 1 will be described. In the reactor ofFIG. 1 a baffle 20 and conduit 22 are provided near the center of thereactor to cause the downwardly flowing body of ore particles toconverge near the center of the reactor. In some cases the nature of theore is such that the particles tend to agglomerate during the reductionstep and in such cases a convergence of the flowing ore bed as providedin the reactor of FIG. 1 could result in obstruction of the flow of oreparticles at the entry of conduit 22. To provide for this contingency,the baffle 20 is eliminated in the reactor of FIG. 2.

Referring to FIG. 2, the reactor 210 comprises a reduction zone 212 andcooling zone 214 similar to the zones 12 andl4 of FIG. 1. The reducinggas is introduced into the reactor through a plenum chamber 224 similarto the chamber 24 and leaves the reactor through a discharge connection252. Cooling gas enters an annular space 228 similar to the annularspace 28 of reactor and flows upwardly through a cooling zone 214.However, reactor 210 differs from reactor 10 in that removal of thecooling gas is effected through an annular plenum chamber 400 ratherthan the annular space 94 of reactor 10.

In the embodiment of FIG. 2 commingling of the cooling and reductiongases is minimized by approximately equalizing the flow of gas into andremoval of gas from the cooling zone. In FIG. 2 a flow controller 282similar to flow controller 82 of FIG. 1 controls constant the flow ofcooling gas into the cooling gas loop. However, in the system of FIG. 2the pressure controller 126 of FIG. 1 is replaced by a flow controller402 which is set to maintain the cooling gas outflow approximately equalto the input as controlled by controller 282, thus maintaining thequantity of cooling gas in the cooling zone substantially constant. Inpractice the controller 402 is ordinarily set to pass a bit more'gasthan controller 282 so that there will be a slight flow of reducing gasfrom the reduction zone to the cooling zone, thereby ensuring that thereducing gas will not be contaminated by a flow of cooling gas into thereduction zone. On the other hand, in particular cases it may bedesirable to avoid contamination of the cooling gas by the reducinggases and in such cases the controller 402 is set to pass somewhat lessgas than controller 282. The system of FIG. 2, like that of FIG. 1,provides for essentially independent control of the reducing gas andcooling gas streams.

In the embodiments of the present invention shown in FIGS. 1 and 2,counter-current flow of the reducing gas and descending ore particles isemployed andcounter-current flow of the cooling gas is also employed.While such counter-current flow is generally desirable,

there are some instances in which co-current flow of the reducing gasand ore are advantageous. In general, the rate at which the ore isreduced varies directly as a function of the temperature of the reducinggas. It is known that the reducing gas temperature is an especiallyimportant factor in determining the reduction reaction rate in the earlystages of the reduction process. Thus, under certain conditions, byusing co-current flow of the reducing gas and ore, an increase in theaverage reduction rate can be achieved, with the result that a givendegree of reduction can be achieved with a shorter residence time of thesolids in the reduction zone, or a greater degree of reduction can beachieved using the same residence time, all other factors being thesame. Also in some cases cocurrent flow of the cooling gas in thecooling section of the reactor may be desirable.

, In general, the choice as to whether counter-current flow orco-current flow of the reducing gas and ore is used depends upon suchfactors as the solidflow characteristics of the ore particles, thereduceability of the ore, the composition of the reducing gas and theheat transfer characteristics of the gas and ore particles. Thusimproved operating flexibility can be achieved by providing a systemwherein either counter-current or co-current gas flow can be used in thereactor. Such a system is illustrated in FIG. 3 of the drawings.

Since the embodiment of the present invention which permits selectiveuse of counter-current or c'o-current gas flow in the reactor isgenerally similar to the embodiments illustrated in FIGS. 1 and 2, onlythose portions of the system which provide for selective use ofcounter-current or co-current gas flow are illustrated in FIG. 3.Referring to FIG. 3, the reactor 510 is similar to the reactor 210 ofFIG. 2 and comprises a reduction zone 512 in the upper portion thereofand a cooling zone 514 in the lower portion thereof. Referring to theleft-hand portion of FIG. 3, the reducing gas is heated in a heater 548,similar to the heater 48 of FIG. 1, which is connected by a pipe 515containing a valve 517 to the plenum chamber 524 of reactor 510. At apoint near plenum chamber 524 pipe 515 is connected to a branch pipe550, similar to the pipe 50 of FIG. 1.,

containing a valve 551. As in the case of pipe 50, air or oxygen may beadded to the reducing gas stream through pipe 550 to increase thereducing gas temperature to the desired value.

Connected to reactor 510 near the top of reduction zone 512 there is apipe 552, corresponding to pipe 52 of FIG. 1, which contains a valve 519and leads to cooler 554, similar to the cooler 54 of FIG. 1. At a pointnear the top of the reactor, pipe 552 communicates with a branch pipe529 containing a valve 545 through which air or oxygen. can be suppliedto pipe 552.

In order to provide for co-current flow of the reducing gas and ore inthe reduction zone 512, when desired, pipe 515, at a'point betweenheater 548 and valve 517, is connected by a pipe 521 containing a valve523 to pipe 552 at a point between reactor 510 and valve 519. Also pipe515, at a point between valve 517 and chamber 524, is connected by apipe 525 containing valve 527 with pipe 552 at a point between valve 519and cooler 554.

In cases where counter-current flow of the reducing gas and ore isdesired, valves 523, 527 and 545 are closed, valves 517 and 519 areopened and valve 551 is opened to an extent sufficient to allow adesired flow of air or oxygen into pipe 515. Reducing gas then flowsfrom heater 548 through pipe 515 to chamber 524 and thence upwardlythrough the ore body in reduction zone 512. The reducing gas leaves thereactor near the top of the reduction zone 512 and flows through pipe552 to cooler 554.

In cases where co-current flow of the reducing gas and ore are desired,valves 517, 519 and 551 are closed, valves 523 and 527 are opened andvalve 545 is opened to such an extent as to establish a desired flow ofair or oxygen into pipe 552. Reducing gas from heater 548 then flowsthrough pipes 521 and 552 to the top of the reduction zone 512 anddownwardly through the ore body therein. The reducing gas leaves thereduction zone through plenum chamber 524 and flows through pipes 515,525 and 552 to the cooler 554. Thus counter-current flow of gas and oreis achieved in a simple manner by closing valves 523 and 527 and openingvalves 517 and 519, and co-current flow is achieved by closing valves517 and 519 and opening valves 523 and 527.

As shown in the lower portion of FIG. 3, a similar arrangement isprovided for selectively establishing either counter-current orco-current flow of the cooling gas in the cooling zone 514 of thereactor. The cooling gas is supplied to the system through a pipe 580and flows through a flow controller 592, similar to the flow controller92 of FIG. 1, and thence through a pipe 590 containing valve 531 andconnected to the chamber 528 at the bottom of cooling zone 514. At thetop of the cooling zone 514 there is a plenum chamber 500, similar tothe chamber 400 of FIG. 2, which is connected by a pipe 596 containingvalve 533 to the dust separator 598, which corresponds with the dustseparator 98 of FIG. 1. In order to provide for co-current flow of thecooling gas through cooling zone 514, pipe 590 at a point between valve531 and flow controller 592 is connected by a pipe 535 containing valve537 with pipe 596 at a point between valve 533 and plenum chamber 500.Also pipe 590 at a point between valve 531 and chamber 528 is connectedby a pipe 539 containing valve 541 to pipe 596 at a point between valve533 and dust separator 598.

When it is desired to establish counter-current. flow in the coolingzone, valves 531 and 533 are opened and valves 537 and 541 are closed.Cooling gas then flows through pipe 590 to chamber 528, upwardly throughthe cooling zone to chamber 500 and'out of the reactor through pipe 596to dust separator 598. On the other hand, when it is desired toestablish co-current flow of the cooling gas and ore in cooling zone514, valves S31 and 533 are closed and valves 537 and 541 opened tocause the cooling gas to flow from flow controller 592 through pipes 535and 596 to plenum chamber 500 and thence downwardly through the ore bodyin the cooling zone. The cooling gas after passing through the coolingzone enters chamber 528 and flows through pipes 590, 539 and 596 to dustseparator 598. It is evident that with the system illustrated in FIG. 3either countercurrent or co-current flow of the gas may be establishedin either the reduction zone or the cooling zone of the system.

In the system shown in FIG. 3 intermingling of the reducing gas andcooling gas is minimized in the same manner as described in connectionwith FIG. 2. The flow of cooling gas to the cooling gas loop iscontrolled constant by a flow controller (not shown in FIG. 3 butcorresponding to the controller 282 of FIG. 2). Cooling gas leaving thecooling gas loop flows through pipe 504, corresponding to pipe 304 ofFIG. 2, to the flow controller 502, corresponding to the flow controller402 of FIG. 2. The flow controller 502 is set to maintain the flow ofcooling gas removed from the system substantially equal to the flow ofcooling gas into the system and thereby minimizes intermingling of thecooling gas and reducing gas.

It is, of course, to be understood that the foregoing description isintended to be illustrative and that the embodiments described can bemodified in various ways within the scope of the invention. For example,the reducing gas employed need not be made in a catalytic reformer ofthe type illustrated at 30, but may be made, for example, by the partialoxidation of a hydrocarbon, or pure hydrogen may be used. The gas heater48 may be so operated as to bring the reducing gas to an acceptablereducing temperature without addition of air or oxygen through pipe 50.Since the cooling gas is heated in the zone 14, if reactive gases areused as coolants, they may be reformed to such an extent that,

- after removal from the cooling loop, they may be advantageouslyintroduced into the reducing gas stream. However, the composition andflow rate of the cooling gases should desirably be selected to achievethe primary function of efficient cooling and any reducing value of thespent cooling gas treated as an incidental advantage of the system.

As indicated above, independent control of both the reducing gas andcooling gas streams can be achieved without recycling these streams.However, the use of the closed loops is preferable becuase of theeconomies thereby obtained and because a greater degree of stability ofthe system is achieved and the minimizing of the commingling of the twostreams is facilitated.

Further, as pointed out at the beginning of the specification, thepresent method and apparatus may be used'in the reduction of ores otherthan iron ore, for example, ores of metals such as nickel, copper, tin,titanium, barium and calcium.

Other modifications within the scope of the invention will be apparentto those skilled in the art.

We claim:

1. The method of reducing particulate metal ores to metal particles in avertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate metal ore inthe upper portion of said bed and a cooling zone for cooling the reducedmetal particles in the lower portion of said bed, feeding a hot reducinggas to one point in said reduction zone and causing it to flow throughparticulate ore in said reduction zone to a second spaced point in saidreduction zone, removing said reducing gas from said reactor at saidsecond point in said reducing zone, circulating a cooling gas in aclosed loop including said cooling zone and a conduit external to saidreactor containing a cooler for cooling said circulating cooling gas,feeding cooling gas at a predetermined rate to the externalportion ofsaid loop, venting cooling gas at a regulated rate from the externalportion of said loop, measuring the pressure difference between thebottom of said reduction zone and the top of said cooling zone andregulating the rate at which gas is vented from said cooling gas loop tomaintain said measured differential pressure substantially zero andthereby minimize mixing of said cooling gas and reducing gas in saidreactor.

2. A method according to claim 1 wherein said reducing gas is fed tosaid reactor at a point near the bottom of said reduction zone andremoved from said reactor at a point near the top of said reductionzone.

3. A method according to claim 1 wherein said reducing gas is fed tosaid reactor at a point near the top of said reduction zone and removedfrom said reactor at a point near the bottom of said reduction zone.

4. A method according to claim 1 wherein said cooling gas is fed to saidreactor at a point near the bottom of said cooling zone and removed fromsaid reactor at a point near the top of said cooling zone.

5. A method according to claim 1 wherein said cooling gas is fed to saidreactor at a point near the top of said cooling zone and removed fromsaid reactor at a point near the bottom of said cooling zone.

6. A method according to claim 1 wherein a portion of the reducing gasremoved from said reactor is added to the reducing gas fed to saidreactor to form a reducing gas loop and the remainder of the reducinggas removed from said reactor is continuously removed from said loop.

7. A method according to claim 1 wherein said cooling gas is a reducinggas and at least a regulated portion of the cooling gas vented from saidcooling gas loop is added to the reducing gas fed to said reductionzone.

8. The method of reducing particulate metal ores to metal particles in avertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate metal ore inthe upper portion of said bed and a cooling zone for cooling the reducedmetal particles in the lower portion of said bed, circulating a reducinggas in a closed loop including said reduction zone and a conduitexternal to said reactor, feeding reducing gas at a predetermined rateto the external portion of said reducing gas loop, venting reducing gasat a regulated rate from the external portion of said reducing gas loop,regulating the flow of at least a portion of the reducing gas ventedfrom said reducing gas loop in response to the pressure at the bottom ofsaid reduction zone to maintain the pressure at the bottom of saidreduction zone substantially constant, circulating a cooling gas in aclosed loop including said cooling zone and a conduit external to saidreactor containing a cooler for cooling said circulating cooling gas,feeding cooling gas at a predetermined rate to the external portion ofsaid loop, and venting cooling gas from the external portion of saidloop at a regulated rate approximately the same as the rate at whichcooling gas is fed to the external portion of said loop to minimizemixing of said cooling gas and said reducing gas in said reactor.

9. The method of reducing particulate iron ore to sponge iron in avertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate iron ore tosponge iron particles in the upper portion of said bed and a coolingzone for cooling the sponge iron particles in the lower portion of saidbed, feeding a hot reducing gas to a point in the reduction zone andcausing it to flow through the particulate iron ore in said reductionzone to a second spaced point in said reduction zone, removing saidreducing gas from said reactor at said second point in said reducingzone, circulating a cooling gas in a closed loop including said coolingzone and a conduit external to said reactor containing a cooler forcooling said circulating cooling gas, feeding cooling gas at apredetermined rate to the external portion of said loop, venting coolinggas at a regulated rate from the external portion of said loop,measuring the pressure difference between the bottom of said reductionzone and the top of said cooling zone and regulating the rate at whichgas is vented from said cooling gas loop to maintain said measureddifferential pressure substantially zero and thereby minimize mixing ofsaid cooling gas and reducing gas in said reactor.

10. The method of reducing particulate metal ores to metal particles ina vertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate metal ore inthe upper portion of said bed and a cooling zone for cooling the reducedmetal particles in the lower portion of said bed, feeding a hot reducinggas to one point in said reduction zone and causing it to flow throughparticulate ore in said reduction zone to a second spaced point in saidreduction zone, removing said reducing gas from said reactor at saidsecond point in said reducing zone, circulating a cooling gas in aclosed loop including said cooling zone and a conduit external to saidreactor containing a cooler for cooling said circulating cooling gas,feeding cooling gas at a predetermined rate to the external portion ofsaid loop, and venting cooling gas from the external portion of saidloop at a regulated rate approximately the same as the rate at whichcooling gas is fed to the external portion of said loop to minimizemixing of said cooling gas and said reducing gas in said reactor.

11. A method according to claim 10 wherein said reducing gas is fed tosaid reactor at a point near the bottom of said reduction zone andremoved from said reactor at a point near the top of said reductionzone.

12. A method according to claim 10 wherein said reducing gas is fed tosaid reactor at a point near the top of said reduction zone and removedfrom said reactor at a point near the bottom of said reduction zone.

13. A method according to claim 10 wherein said cooling gas is fed tosaid reactor at a point near the bottom of said cooling zone and removedfrom said reactor at a point near the top of said cooling zone.

14. A method according to claim 10 wherein said cooling gas is fed tosaid reactor at a point near the top of said cooling zone and removedfrom said reactor at a point near the bottom of said cooling zone.

15. A method according to claim 10 wherein at least a part of thereducing gas removed from said reactor is recycled and added to thereducing gas fed to said reactor to form a reducing gas loop and theremaining reducing gas is continuously removed from said loop.

16. A method according to claim 10 wherein said cooling gas is areducing gas and at least a regulated portion of the cooling gas ventedfrom said cooling loop is added to the reducing gas fed to saidreduction zone.

17. A method according to claim 10 wherein the cooling gas is ventedfrom said cooling loop at a rate slightly greater than the predeterminedrate at which it is fed to said loop.

18. A method according to claim 7 wherein the cooling gas is vented fromsaid cooling gas loop at a rate slightly less than the predeterminedrate at which it is fed to said loop.

19. The method of reducing particulate metal ores to metal particles ina vertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate metal ore 'inthe upper portion of said bed and a cooling zone for cooling the reducedmetal particles in the lower portion of said bed, feeding a hot reducinggas to a point near one end of said reduction zone and causing it toflow through particulate ore in said reduction zone to the other end ofsaid reduction zone, removing said reducing gas from said reactor at apoint near said other end of said reducing zone, circulating a coolinggas in a closed loop including said cooling zone and a conduit externalto said reactor containing a cooler for cooling said circulating coolinggas, feeding cooling gas at a predetermined rate to the external portionof said loop, venting cooling gas at a regulated rate from the externalportion of said loop, measuring the pressure difference between thebottom of said reduction zone and the top of said cooling zone andregulating the rate at which gas is vented from said cooling gas loop tomaintain said measured differential pressure substantially zero andthereby minimize mixing 'of said cooling gas and reducing gas in saidreactor.

20. The method of reducing particulate metal ores to metal particles ina vertical shaft, moving bed reactor which comprises establishing andmaintaining a reduction zone for reducing said particulate metal ore inthe upper portion of said bed and a cooling zone for cooling the reducedmetal particles in the lower portion of said bed, circulating a reducinggas in a closed loop including said reduction zone and a conduitexternal to said reactor, feeding reducing gas at a predetermined rateto the external portion of said reducing gas loop, venting reducing gasat a regulated rate from the external portion of said reducing gas loop,circulating a cooling gas in a closed loop including said cooling zoneand a conduit external to said reactor containing a cooler for coolingsaid circulating cooling gas, feeding cooling gas at a predeterminedrate to the external portion of said cooling gas loop, venting coolinggas at a regulated rate from the external portion of said cooling gasloop, regulating the flow of at least a portion of the reducing gasremoved from said reducing gas loop in response to the pressure at thebottom of said reduction zone to maintain the pressure at the bottom ofsaid reduction zone substantially constant, measuring the pressuredifference between the bottom of said reduction zone and the top of saidcooling zone and regulating the rate at which gas is vented from saidcooling gas loop to maintain said measured differential pressuresubstantially zero and thereby minimize mixing of said cooling gas andreducing gas in said reactor.

2. A method according to claim 1 wherein said reducing gas is fed tosaid reactor at a point near the bottom of said reduction zone andremoved from said reactor at a point near the top of said reductionzone.
 3. A method according to claim 1 wherein said reducing gas is fedto said reactor at a point near the top of said reduction zone andremoved from said reactor at a point near the bottom of said reductionzone.
 4. A method according to claim 1 wherein said cooling gas is fedto said reactor at a point near the bottom of said cooling zone andremoved from said reactor at a point near the top of said cooling zone.5. A method according to claim 1 wherein said cooling gas is fed to saidreactor at a point near the top of said cooling zone and removed fromsaid reactor at a point near the bottom of said cooling zone.
 6. Amethod according to claim 1 wherein a portion of the reducing gasremoved from said reactor is added to the reducing gas fed to saidreactor to form a reducing gas loop and the remainder of the reducinggas removed from said reactor is continuously removed from said loop. 7.A method according to claim 1 wherein said cooling gas is a reducing gasand at least a regulated portion of the cooling gas vented from saidcooling gas loop is added to the reducing gas fed to said reductionzone.
 8. The method of reducing particulate metal ores to metalparticles in a vertical shaft, moving bed reactor which comprisesestablishing and maintaining a reduction zone for reducing saidparticulate metal ore in the upper portion of said bed and a coolingzone for cooling the reduced metal particles in the lower portion ofsaid bed, circulating a reducing gas in a closed loop including saidreduction zone and a conduit external to said reactor, feeding reducinggas at a predetermined rate to the external portion of said reducing gasloop, venting reducing gas at a regulated rate from the external portionof said reducing gas loop, regulating the flow of at least a portion ofthe reducing gas vented from said reducing gas loop in response to thepressure at the bottom of said reduction zone to maintain the pressureat the bottom of said reduction zone substantially constant, circulatinga cooling gas in a closed loop including said cooling zone and a conduitexternal to said reactor containing a cooler for cooling saidcirculating cooling gas, feeding cooling gas at a predetermined rate tothe external portion of said loop, and venting cooling gas from theexternal portion of said loop at a regulated rate approximately the sameas the rate at which cooling gas is fed to the external portion of saidloop to minimize mixing of said cooling gas and said reducing gas insaid reactor.
 9. The method of reducing particulate iron ore to spongeiron in a vertical shaft, moving bed reactor which comprisesestablishing and maintaining a reduction zone for reducing saidparticulate iron ore to sponge iron particles in the upper portion ofsaid bed and a cooling zone for cooling the sponge iron particles in thelower portion of said bed, feeding a hot reducing gas to a point in thereduction zone and causing it to flow through the particulate iron orein said reduction zone to a second spaced point in said reduction zone,removing said reducing gas from said reactor at said second point insaid reducing zone, circulating a cooling gas in a closed loop includingsaid cooling zone and a conduit external to said reactor containing acooler for cooling said circulating cooling gas, feeding cooling gas ata predetermined rate to the external portion of said loop, ventingcooling gas at a regulated rate from the external portion of said loop,measuring the pressure difference between the bottom of said reductionzone and the top of said cooling zone and regulating the rate at whichgas is vented from said cooling gas loop to maintain said measureddifferential pressure substantially zero and thereby minimize mixing ofsaid cooling gas and reducing gas in said reactor.
 10. The method ofreducing particulate metal ores to metal particles in a vertical shaft,moving bed reactor which comprises establishing and maintaining areduction zone for reducing said particulate metal ore in the upperportion of said bed and a cooling zone for cooling the reduced metalparticles in the lower portion of said bed, feeding a hot reducing gasto one point in said reduction zone and causing it to flow throughparticulate ore in said reduction zone to a second spaced point in saidreduction zone, removing said reducing gas from said reactor at saidsecond point in said reducing zone, circulating a cooling gas in aclosed loop including said cooling zone and a conduit external to saidreactor containing a cooler for cooling said circulating cooling gas,feeding cooling gas at a predetermined rate to the external portion ofsaid loop, and venting cooling gas from the external portion of saidloop at a regulated rate approximately the same as the rate at whichcooling gas is fed to the external portion of said loop to minimizemixing of said cooling gas and said reducing gas in said reactor.
 11. Amethod according to claim 10 wherein said reducing gas is fed to saidreactor at a point near the bottom of said reduction zone and removedfrom said reactor at a point near the top of said reduction zone.
 12. Amethod according to claim 10 wherein said reducing gas is fed to saidreactor at a point near the top of said reduction zone and removed fromsaid reactor at a point near the bottom of said reduction zone.
 13. Amethod according to claim 10 wherein said cooling gas is fed to saidreactor at a point near the bottom of said cooling zone and removed fromsaid reactor at a point near the top of said cooling zone.
 14. A methodaccording to claim 10 wherein said cooling gas is fed to said reactor ata point near the top of said cooling zone and removed from said reactorat a point near the bottom of said cooling zone.
 15. A method accordingto claim 10 wherein at least a part of the reducing gas removed fromsaid reactor is recycled And added to the reducing gas fed to saidreactor to form a reducing gas loop and the remaining reducing gas iscontinuously removed from said loop.
 16. A method according to claim 10wherein said cooling gas is a reducing gas and at least a regulatedportion of the cooling gas vented from said cooling loop is added to thereducing gas fed to said reduction zone.
 17. A method according to claim10 wherein the cooling gas is vented from said cooling loop at a rateslightly greater than the predetermined rate at which it is fed to saidloop.
 18. A method according to claim 7 wherein the cooling gas isvented from said cooling gas loop at a rate slightly less than thepredetermined rate at which it is fed to said loop.
 19. The method ofreducing particulate metal ores to metal particles in a vertical shaft,moving bed reactor which comprises establishing and maintaining areduction zone for reducing said particulate metal ore in the upperportion of said bed and a cooling zone for cooling the reduced metalparticles in the lower portion of said bed, feeding a hot reducing gasto a point near one end of said reduction zone and causing it to flowthrough particulate ore in said reduction zone to the other end of saidreduction zone, removing said reducing gas from said reactor at a pointnear said other end of said reducing zone, circulating a cooling gas ina closed loop including said cooling zone and a conduit external to saidreactor containing a cooler for cooling said circulating cooling gas,feeding cooling gas at a predetermined rate to the external portion ofsaid loop, venting cooling gas at a regulated rate from the externalportion of said loop, measuring the pressure difference between thebottom of said reduction zone and the top of said cooling zone andregulating the rate at which gas is vented from said cooling gas loop tomaintain said measured differential pressure substantially zero andthereby minimize mixing of said cooling gas and reducing gas in saidreactor.
 20. The method of reducing particulate metal ores to metalparticles in a vertical shaft, moving bed reactor which comprisesestablishing and maintaining a reduction zone for reducing saidparticulate metal ore in the upper portion of said bed and a coolingzone for cooling the reduced metal particles in the lower portion ofsaid bed, circulating a reducing gas in a closed loop including saidreduction zone and a conduit external to said reactor, feeding reducinggas at a predetermined rate to the external portion of said reducing gasloop, venting reducing gas at a regulated rate from the external portionof said reducing gas loop, circulating a cooling gas in a closed loopincluding said cooling zone and a conduit external to said reactorcontaining a cooler for cooling said circulating cooling gas, feedingcooling gas at a predetermined rate to the external portion of saidcooling gas loop, venting cooling gas at a regulated rate from theexternal portion of said cooling gas loop, regulating the flow of atleast a portion of the reducing gas removed from said reducing gas loopin response to the pressure at the bottom of said reduction zone tomaintain the pressure at the bottom of said reduction zone substantiallyconstant, measuring the pressure difference between the bottom of saidreduction zone and the top of said cooling zone and regulating the rateat which gas is vented from said cooling gas loop to maintain saidmeasured differential pressure substantially zero and thereby minimizemixing of said cooling gas and reducing gas in said reactor.